periodic table std 10, Study notes of Chemistry

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PERIODIC TABLE

Std 10

MODERN PERIODIC LAW

THE PHYSICAL AND CHEMICAL

PROPERTIES OF ELEMENTS ARE

THE PERIODIC FUNCTIONS OF

THEIR ATOMIC NUMBERS.

PERIODS

• First period shortest with only 2 elements.
• Periods 2 & 3 are short with 8 elements each.
• Periods 4 & 5 are long with 18 elements each.
• Period 6 is longest with 32 elements
• Period 7 is incomplete with 26 elements.

GROUP 2 - ALKALINE EARTH METALS

Valence electrons - two

Valency - divalent

Nature - Reactive ,

electropositive metals

GROUP 3 TO 12 - TRANSITION ELEMENTS

INNER TRANSITION ELEMENTS

Lanthanide series and Actinide series

They are all metals , chemically very reactive , lie at the bottom of the periodic table.

GROUP 17 - HALOGENS

Valence electrons : 7

Valency : univalent (1-)

Nature : highly reactive , Electronegative,

nonmetals. Good oxidizing agents

They are non conductors of heat and electricity

GROUP 18 - NOBLE GASES

They have stable electronic configuration, are chemically inert or unreactive.

They are all monatomic gases

Valency : zero

GROUP NUMBER

Group number signifies the number of valence electrons

Eg: Group 1 elements have one valence electron

Group 2 elements have two valence electrons

PERIODIC PROPERTIES

The properties which appear at regular intervals in the periodic table are called periodic properties.

The phenomenon is called periodicity in properties of elements

REASONS FOR PERIODICITY

1. After definite intervals of at. no , similar valence shell electronic configuration occurs.
2. Properties of elements depend on the number and arrangements of electrons in various shells including valence shells.